Locking device for castered airplane main landing wheels



NOV 195] o. w LOUDENSLAGER 1 2,575,761

LOCKING DEVICE FOR CASTERED AIRPLANE MAIN LANDING WHEELS Filed March 11, 1948 2 SHEETS-SHEET 1 INVENTOR. Osqar W, Loudens/ager ATTORNEY Nov. 20, 1951 o. w. LQUDENSLAGER 2,575,761

LOCKING DEVICE FOR CASTERED AIRPLANE MAIN LANDING WHEELS 2 SHEETS-SHEET 2' Filed March 11 1948 w A MM m .7 ym 0 INVENTOR. Oscar h! Loudens/ager A TTORNEY Patented Nov. 20, 1951 LOCKING DEVICE FOR CASTERED AIRPLANE MA N ANDING WHEELS- Osc r W. Loudenslager, kron. Ohio, assienor to Goodyear Aircraft Corporation, Akron, Ohio, a corp oration of Delaware Application March 11, 1948,, Serial No. 14,378

This: invention'relates to the improvement, of the Cross-Wind Airplane Landing Gear, Serial No. 741,198, filed April 14, 1947, now U. S; Patent No. 2,504,077", issued April 11, 1950,. in which the Wheels caster only within a limited angle, and, in particular, to a locking device to prevent castering these wheels when an airplane is moved backward.

Heretofore, it has been known to provide. airplane tail wheels, usuallycastering 360; with arresting or looking devices. These, however, were of a. more complicated construction and did not lock the wheels automatically;

It is. the general object of the invention to overcome the foregoin and other difliculties by providing castering airplane main landing wheels having only limited caster angles with automatic means permitting castering of the wheels at higher speed and locking them: at low speed, for

instance, when the airplane is moved backward to be parked within a restricted space.

Another object of the invention is to achieve automatic locking of castering airplane. main landing wheels in the simplest and cheapest possible way.

The aforesaid objects of the invention and other objects, which will become apparent as the description proceeds, are achieved byproviding the stabilizing or centering cam of the wheel with a. notch at. the lowest portion of the cam surface on, which rides the cam follower. This notch is so designed and dimensioned that the cam follower will not be unseated from the notch when the airplane on the ground moves at low speed, particularly in backward direction, for in- Fig. 1 shown with the bearings and outer bear-- ing ring removed.

Fig; 3 is a fragmentary horizontal cross-sectional view of the wheel axle taken on line IIIIII of Fig. 1.

Fig. 4 is a cross-sectional view taken on line IV--IV of Fig. 5 of a cam inserted at the bottom of the king pin support.

Fig.5isatop plan view of Fig. 4.

1 Claim. (Cl. 244-403) Fig. 6 is a cam end view.

Fig. 7 is a diagrammatic view of; the castering: wheel for explainingthe functioning of the mventlom Figs. 8 and 9 show possible positions. of the wheels; in. backward motion when without the provision of the locking device.

Although the principles of the invention have been found particularly applicable for light airplanes, there is no apparent limit to their application for land. airplanes in general.

With. specific referencev to the drawings, the numeral I. indicates, in general, a castered main wheel; for an airplane consisting of a rubber tire 2- inserted between the. rim parts: 3 and 4 having a number of spacers 5 and B, respectively, distributed over the. circumference, against which the outer bearing supports 1 and 8 are clamped by bolts 9. Roller bearings I0 inserted with their outer races. into the bearing supports 1 and 8 have. fitted between and within their inside races a. non-rotatable hub H which carries a. king pin l2? passing through the center thereof and being secured thereto by a washer l3 and a cotter pin M- Through a transverse open ing I 5 in. the king pin support H passes, spaced from the inner side walls thereof, the wheel stub axle Ifi attached to the airplane landing frame 11,. and in. the outerend of which the king pin l2; pivots allowing the wheel to caster about. 25 degrees to. either side from its center position, i. e., avertical. plane parallel to the longitudinal axis of, the. airplane.

Into the bottom portion of the opening I5 is fitted. a. circular cam l8: (shown enlarged, Figs. 4:. to; 6:), having sharper contoured diametrically opposite notches 3| at thev bottom. of its upweirdly-directed, flatly-notched active surfaces 32 and. being concentric to the kin pin I2. The cam: l8. held. under pressure of the spring I 9 in the recess 20, cooperates with a set of oppositely arranged" cam followers. 21 extending from the underside of thestub axle [6- to return the wheel from a. casterecl. position. to zero or normal position, The sharper notches 3!, in which. are seated the: cam followers 21', prevent the wheel from castering at lowspeed in backward movement, but will permit it at higher speed in forward movement for taxiin and landing purposes. Therefore, when moving the airplane backward as, for instance, for parking it within a restricted area, as in a hangar, the wheels are always kept in straight or zero position, because at such low speed a side force will not cause the cam followers 2| to be unseated from the notches 3|.

Furthermore, as indicated in Fig. 7, the vertical 4 been found that a castering angle of 25 degrees in either direction from the zero position of the wheel, i. e., a vertical plane parallel to the longitudinal axis of the airplane, is ample to safely land and to take-off an airplane in a 90 degree side wind of about 30 miles an hour. This angle, however, may be varied somewhat for different type of airplanes; and, also, the angle of about 21 degrees between the king pin axis and the vertical which was found suitable may be increased or decreased in specific installations.

cannot unseat the cam followers 2| from the notches 3| and, thus, makes this arrangement a workable automatic device for locking the wheels against castering for such purpose. successfully proved by many tests made. 7 Figs. 8 and 9 show the landing wheels in intoed andout-toed position, respectively, which they might assume with a negative caster "and which would interfere with proper ground handling of the airplane. As seen in Fig. 2 the king pin 12 is positioned at an angle to the vertical so that even with a raised tail end of an airplane the intersection of 'the king pin axis with the ground is always forward of the wheel ground contact to provide in forward motion at sufficient speed positive ca's'ter action of the wheel. In casterin the wheel the cam followers sweeping over the cam will tend to lift the airplane about the same amount'as the loss of wheel height due to the change of the vertical position of the wheel into a leaning position (because of the angle of king pin with the vertical), thus keeping the plane always at the substantially same height. It is to be noted that when the airplane is on the ground the cam I8 and cam followers 2| are held together by the weight of the airplane. T

In Fig. 3 are shown by dash lines the extreme angular positions of the wheel to which it can swin out in both directions, that is, until the inner broken edges of the king pin support H will touch the stub axle [6. The cam l81shown by itself in Figs. 4, 5 and 6 is rather-low to enable the wheel at sufficient speed to overcome the locking effect of the cam notch 3| and to caster in either direction with little effort which makes castering a smooth operation to avoid jerks and reduce shimmying. Also, because of the sym metrical shape of the cam, it will readily bring back the wheel, when oil the ground, to its zero position, that is parallel to the longitudinal axis of the airplane. I

In order to dampen smaller lateral wheel motions or secondary vibrations due to uneven ground a friction element 22 is provided, having at its inner side a cylindrical surface 23 equidis tant to the king pin axis against which is pressed, by a spring 24, a preferably cylindrical friction block 25.

'A standard spot disk brake, indicated as a whole at 26, is attached by bolts 21 to the inner side of the king pin support I I to cooperate with the brake disk 28 held by keys 29 fastened -to the brake flange 30 integral with the wheel'ri'm 4. A brake of this type is especially suitable, as in this case, the available space is limited. In operating this type of landing gear it has That was It will be recognized that the objects of the invention have been achieved by an extremely simple structural change of the original construction by automatically locking castering of the wheels at low speed, as, for instance, for parking,

but let them caster freely at higher speed for V taxiing and landing maneuvers.

While in accordance with the patent statutes one best known embodiment of the invention has been illustrated and described in detail, it is to be particularly understood that the invention is not'limited thereto or thereby, but that the in-- ventive scope is defined in the appended claim.

I claim:

A cross-wind main landing gear for an airplane including a horizontal transverse axle, a king pin pivotally and slidably positioned in each end, of

the axle in vertical planes parallel to the lon-' gitudinal airplane axis and at an angle with the vertical, a hollow hub fixedly mounted-on each king pin and being radially spaced from the axle for allowing the hub castering movement to about'25 on each side of the aforesaid vertical planes, a spring inserted between hub and axle for resilient movement of the axle with respect to the king pin, a Wheel rotatably'mounted on the hub, a fiat low cam seated on the hub concentrica'lly to the king pin, said cam having a pair of symmetrically arranged annular up wardly-facing friction surfaces of concavelycurved contours extending over the 25 castering movement and including a low-depth radial notch at the bottom of each friction surface and having a cross-sectional curvature somewhat REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,896,234 Hathorn Feb. 7, 1933 2,326,019 Dowty Aug. 3, 1943 FOREIGN PATENTS Number Country Date Great Britain Jan. 21, 1942 

